Multiple PHP versions.

Is there a good way to run multiple PHP versions with ISPConfig3? I have an old webmail client which my client wants to keep and does not want to pay to upgrade to the latest version which only supports PHP < 5.3.

The ispconfig part is easy, you just add the path to the new php binary in the interface. What might be more complicated is to built a php binary of the desired php version, this differs for each linux distribution but most likely you will have to compile it.